In a message dated 3/26/00 7:19:07 AM Pacific Standard Time,
aeb1(at)americanisp.net writes:
<< Note that these should be GRADE 8 or better replacement bolts! -art-
>>
Art,
I sent an original bolt thru the non-destructive testing lab at a certain
unnamed major commercial airplane manufacturer here in Seattle to determine
what was causing the failures. The mild steel washer is at fault, and the
metalurgist recommended an aviation graded bolt with an automotive rated
hardness factor of about grade 6.5. I sold that exact bolt in my carrier
bolt replacement kit for years, and there was never a failure, even in
extreme stress roadracing applications.
There are other contributing reasons for the failures as well, such as
the shortness of the original bolt which does not utilize the depth of the
threaded hole in the crown gear and the short shank which puts the shearing
load across the threaded shaft of the bolt, rather than the smooth shank near
the head. My aviation bolts resolved all three issues, and the washer set I
supplied were as Rootes blueprints show and not what they installed.
Although they are more brittle and have a short shank, common grade 8 bolts
will work fine...but at least use a hardened washer and locktite!
Jim Leach PTC Seattle
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